Sweet Potato Steamed Buns (Bao)

Name: Sweet Potato Steamed Buns (Bao)
Prep time: 30 min
Total time: 30 min
Cuisine: Asian
Ingredients: 1 and 1/2 cup bao flour; 1/2 cup water; 2 tbsp sugar; 2 tsp oil; 1/2 tsp dry yeast; 1/4 tsp salt; 2 tbsp oil; 1 shallot (minced); 1 tbsp minced lemongrass; 1 clove of garlic (minced); 2 tbsp chopped green onions; 1/4 tsp chopped red chili ((optional, only if you like it spicy)); 1 tbsp dry wood ear mushrooms (soaked in hot water for 10 minutes); 2 dry shiitakes (soaked in hot water for 10 minutes); 1 medium sweet potato (shredded and then cut into 1/2-inch shreds); 1 tbsp soy sauce; 2 tbsp water; 1 tsp cornstarch; 1 tsp sugar; 1/8 tsp ground black pepper (or more to taste)